CODEWITHSUNDEEP
swiftenumsclosuresenumeration
Eric33187
Eric33187

Reputation: 1156

Can a Swift enum have a function/closure as a raw value?

I know an enum can have a closure as an associated value, such as:

enum SomeEnum {
    case closureOne (String, Double -> Double)
    case closureTwo (String, (Double, Double) -> Double)
}

But, can an enum have a closure as a raw value? For instance, does something like this work?

enum someEnum: () -> Void {
    case closureOne = doSomething
    case closureTwo  = doSomethingElse
}

where

let doSomething = {
    // Do something here.
}

let doSomethingElse {
    // Do something else here.
}

Upvotes: 0

Views: 834

Answers (1)

timbre timbre
timbre timbre

Reputation: 14005

It's not as straight forward, but you could use OptionSet, see this page:

Unlike enumerations, option sets provide a nonfailable init(rawValue:) initializer to convert from a raw value, because option sets don’t have an enumerated list of all possible cases. Option set values have a one-to-one correspondence with their associated raw values.

Could be something like this:

func doSomething() {}
func doSomethingElse() {}

struct MyClosures: OptionSet {

    static let closureOne = MyClosures(rawValue: doSomething)
    static let closureTwo = MyClosures(rawValue: doSomethingElse)

    let rawValue: () -> Void

    init(rawValue: @escaping () -> Void) {
        self.rawValue = rawValue
    }

    init() {
        rawValue = {}
    }

    mutating func formUnion(_ other: __owned MyClosures) {
        // whatever makes sense for your case
    }

    mutating func formIntersection(_ other: MyClosures) {
        // whatever makes sense for your case
    }

    mutating func formSymmetricDifference(_ other: __owned MyClosures) {
        // whatever makes sense for your case
    }

    static func == (lhs: MyClosures, rhs: MyClosures) -> Bool {
        // whatever makes sense for your case
        return false
    }
}

And so you can use it as:

let myClosures: MyClosures = [ .closureOne, .closureTwo ]

HOWEVER looking at your explanation in the comment:

So I'm trying to find the most efficient way to run a function given the state of a variable.

I think what you actually want is some sort of state machine. Some examples are available here and here

Upvotes: 2

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